An elevator has a governor that constantly monitors the rising/descending speed of a car and emergency stops the car when the car falls into a predetermined overspeed state. Specifically, when the rising/descending speed of the car exceeds the rated speed and reaches a first overspeed (usually, about 1.3 times the rated speed), the governor shuts off the power supply of a driving device for driving the car and the power supply of a control unit for controlling the driving device. Also, when the descending speed of the car exceeds the first overspeed and reaches a second overspeed (usually, about 1.4 times the rated speed) from any cause, the governor activates a safety gear device provided on the car to emergency stop the car mechanically.
On the other hand, in the case where the rated speed at the descending time must be equal to or lower than a predetermined value due to the restriction of shaft pit depth, in the case where the rated speed at the descending time cannot be increased to restrain a sense of discomfort caused by sudden pressure fluctuations in the car at the time of high-speed operation, or in the like cases, it is also demanded that the elevator be provided with rated speeds different between the rising time and the descending time. To meet such a demand, there has also been proposed a governor capable of providing first overspeeds different between the rising time and the descending time (for example, refer to Patent Document 1).
Patent Document 1 describes the following governors as specific examples.
(1) A governor in which a fly ball type governing mechanism and a fly weight type governing mechanism each having a different first overspeed are provided, and when the elevator car rises, the fly ball type governing mechanism in which the first overspeed is set on the low speed side is separated by a clutch mechanism.
(2) A governor in which two fly weight type governing mechanisms having different first overspeeds are provided, and when the elevator car rises, one governing mechanism in which the first overspeed is set on the low speed side is separated by a clutch mechanism.
(3) A governor in which two fly ball type governing mechanisms having different first overspeeds are provided, and when the elevator car rises, one governing mechanism in which the first overspeed is set on the low speed side is separated by a clutch mechanism.
(4) A governor in which one governing mechanism is provided with a stop switch that is actuated at the first overspeed on the high speed side and a stop switch that is actuated at the first overspeed on the low speed side, and when the elevator car rises, the stop switch set to the low speed side is inactivated by an electric circuit.
(5) A governor in which a moving mechanism for moving the position of a stop switch according to the rising/descending direction of the car is provided, and when the elevator car rises, the stop switch is placed so as to be actuated at the first overspeed on the high speed side, and when the elevator car descends, the stop switch is placed so as to be actuated at the first overspeed on the low speed side.    Patent Document 1: Japanese Patent Laid-Open No. 2000-327241